Polymerization process using a catalyst comprising a phosphate and with a bis-(cyclopentadienyl)chromium(II) compound

ABSTRACT

In accordance with one embodiment of this invention, a bis-(cyclopentadienyl)chromium(II) compound is introduced onto an activated phosphate-containing support and utilized in conjunction with an organometal cocatalyst, such as an alkylaluminum. In accordance with another embodiment of this invention, a phosphate-containing xerogel is formed by removing water from an aluminum phosphate-containing hydrogel by means of azeotropic distillation or washing with a volatile, water miscible organic compound, activated and thereafter a bis-(cyclopentadienyl)chromium(II) compound is incorporated therewith. In other embodiments of this invention, a phosphate-containing support is formed by forming aluminum phosphate from an aluminum alkoxide or from a melt, or by phosphating silica or alumina, or by forming an aluminum phosphate/silica combination. A support thus formed is activated and a bis-(cyclopentadienyl)chromium(II) compound added. Alternatively in all embodiments, the chromium and phosphate components can be added separately. The resulting catalysts are capable of giving narrow molecular weight distribution polymer because of the inherent high molecular weight of the polymer produced, and the unusual sensitivity to hydrogen, a broad spectrum of polymers can be produced so far as molecular weight is concerned. The catalyst is ideally suited for forming olefin polymers such as ethylene and ethylene copolymers in a slurry system.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional of copending application Ser. No. 363,681, filedMar. 30, 1982, now U.S. Pat. No. 4,424,139.

BACKGROUND OF THE INVENTION

This invention relates to phosphate-containing chromium catalyst systemsfor olefin polymerization.

Supported chromium catalysts can be used to prepare olefin polymers in ahydrocarbon solution to give a product having excellent characteristicsfrom many standpoints. Silica supported chromium catalysts can also beused to prepare olefin polymers in a slurry system wherein the polymeris produced in the form of small particles of solid material suspendedin a diluent. This process, frequently referred to as a particle-formprocess, has the advantage of being less complex. However, certaincontrol operations which are easily carried out in the solution processare considerably more difficult in the particle-form process. Forinstance, in the solution process, control of the molecular weight canbe effected by changing the temperature with lower molecular weight(higher melt flow) being obtained at the higher temperature. However, inthe slurry process, this technique is inherently limited since anyefforts to increase the melt flow to any appreciable extent byincreasing temperature would cause the polymer to go into solution andthus destroy the slurry or particle-form process. It is known to extendthe range of melt flow capability of a given catalyst through the use ofhydrogen. However, it has not heretofore been commercially feasible toproduce a complete spectrum of polymers, so far as melt flow isconcerned, in a slurry system with a single chromium catalyst system.

Also it is frequently desired to have a polymer with narrower molecularweight distribution than is normally obtained in the slurry orparticle-form process.

There would be certain advantages to utilizing chromium which does notrequire activation in supported chromium olefin polymerization catalystsystems in that there are some problems associated with calcining a basealready containing chromium. However, the only supported chromium olefinpolymerization systems to achieve commercial success have been those inwhich chromium is supported on silica and the resulting combination iscalcined. This is because of the very low activity associated with othersupported systems. Thus olefin polymerization using the chromiumcatalyst system is still carried out utilizing calcined chromium on asilica-containing base in a manner similar to that used decades ago whenthe chromium catalyzed polymerization of olefin polymers first becamecommercial.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a catalyst capable ofgiving narrow molecular weight distribution;

It is a further object of this invention to provide a catalyst suitablefor use in slurry polymerization systems;

It is yet a further object of this invention to provide a catalystcapable of giving polymer suitable for injection molding and otherapplications requiring narrow molecular weight distribution.

It is yet a further object of this invention to provide a singlecatalyst system capable of giving a broad spectrum of polymers so far asmelt flow is concerned;

It is a further object of this invention to provide an improvedphosphate-containing π-bonded chromium catalyst system for olefinpolymerization;

It is a further object of this invention to provide a novel ultrahighmolecular weight polymer having a high degree of methyl branching;

It is yet a further object of this invention to produce a novel narrowmolecular weight distribution polymer having a high degree of methylbranching;

It is yet a further object of this invention to provide a catalystsystem having unusual sensitivity to molecular weight control agentssuch as hydrogen; and

It is still yet a further object of this invention to avoid the problemsassociated with calcining chromium containing supports.

In accordance with one embodiment of this invention, abis-(cyclopentadienyl) chromium(II) compound and an activatedphosphate-containing composition are utilized in conjunction with anorganometal cocatalyst. In accordance with another embodiment of thisinvention, the phosphate-containing xerogel is formed by removing waterfrom an aluminum phosphate hydrogel by means of azeotropic distillationor washing with a volatile water miscible organic compound, activatedand thereafter is combined with a bis-(cyclopentadienyl)chromium(II)compound. In accordance with other embodiments of this invention, aphosphate-containing support for a bis-(cyclopentadienyl)chromium(II)compound is formed by: forming aluminum orthophosphate from an aluminumalkoxide or from a melt, phosphating silica or alumina, or by forming anAlPO₄ /silica composition.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings forming a part hereof,

FIG. 1 shows the relationship between activation temperature for thesupport and producitivity;

FIG. 2 compares the polymerization rate as a function of time for aninvention catalyst and a zerovalent chromium catalyst; and

FIG. 3 shows the effect of hydrogen on molecular weight distribution.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The base or support can be formed in a number of ways. Four methods ofpreparing the support are set out hereinbelow under the headings MethodA, Method B, Method C and Method D.

Method A. The support of Method A is at least predominantly amorphousaluminum orthophosphate. In accordance with Method A, thephosphate-containing support can be formed using three separatetechniques. First, conventional techniques as disclosed in Hill et al,U.S. Pat. No. 4,219,444, the disclosure of which is hereby incorporatedby reference can be used. In this technique an aluminum salt is combinedwith a source of phosphate ions in an aqueous medium and neutralizedwith a base to give a hydrogel. Alternatively, a polar organic solventcan be used. The second technique for forming the base of Method A is tocombine a hydrolyzable organoaluminum compound such as an aluminumalkoxide as disclosed in Pine, U.S. Pat. No. 3,904,550, the disclosureof which is hereby incorporated by reference, with orthophosphoric acidto give a xerogel directly.

In accordance with the third technique of Method A, an aluminumphosphate gel is formed from a concentrated mass of reactants comprisingaluminum ions from an aluminum salt and a source of orthophosphate ions.This is done by using an aluminum salt which will melt, preferably onewhich will melt at or below the boiling point of water or by forming asyrup of a water soluble aluminum salt and a very small amount of water.

Generally, hydrated aluminum salts such as hydrated aluminum nitrate aremost susceptible to being melted and thus are preferred as the source ofaluminum ions for the melt method. Aluminum bromide and hydratedaluminum bromate can also be used as can, broadly, any aluminum saltwhich will melt. If desired up to 40 weight percent, more generally upto 20 weight percent additional water can be present based on the weightof the aluminum salt or there can be no water except the water, if any,from the water of hydration and the water, if any, from the base used inthe subsequent neutralization, i.e., no extraneous water is added. Byadditional water is meant water actually added as water and does notcount the water, if any, from the water of hydration of the ingredientsand/or the water from the base, if any. There may be some advantage toadding 1 to 15 weight percent water based on the weight of the aluminumsalt, however. The percentages of water are based on the actual weightof the aluminum salt including any water of hydration.

Alternatively, an aluminum salt which will not necessarily melt butwhich will dissolve enough to form a syrup in 40 weight percent, orless, water based on the weight of the aluminum salt can be used.Generally, 5 to 20 weight percent water is used based on the weight ofthe aluminum salt when a syrup is formed. Aluminum sulfate, for instanceis ideally suited for use in this embodiment of the invention.

The source of the phosphate ions can be any source of orthophosphateions and is generally orthophosphoric acid or orthophosphates, such asmonobasic ammonium phosphate or dibasic ammonium phosphate or mixturesthereof.

The temperature, if a melt is used, can be any temperature at or abovewhich the aluminum salt chosen will melt. The reaction can be carriedout in any atmosphere including air or can be carried out under an inertatmosphere for instance. Generally, temperatures of 65°-200° C.,preferably 65°-100° C. are used. Although, since the preferred aluminumsalt is Al(NO₃)₃.9H₂ O which melts at 73° C., the most preferredtemperature based on the use of this aluminum salt is about 80° C.±5° C.If a very concentrated syrup of a water soluble aluminum salt and waterare used, any temperature up to the boiling point of the water under theconditions employed can be used, preferably 20°-100° C.

One of the advantages of this technique is that, since very littlewater, if any, is present during the formation of the aluminumphosphate, it is not necessary to utilize azeotropic distillation orwashing with a normally liquid water miscible organic solvent to removethe water gently. The most important advantage, however, is that theconcentrated mass gives a gel with greater physical strength. If verymuch water is present, the use of the water miscible organic solvent ispreferred and it can be used in all cases.

Low pore volume hydrogels usually give the highest porosity xerogelsafter drying because they have superior internal strength to withstandthe compression of surface tension. Thus, if the hydrogel occupies 6 ccper gram of aluminum phosphate or less, generally 3 to 6 cc per gram, itwill give a xerogel having improved porosity for a catalyst base thanwill a hydrogel conventionally prepared from a dilute aqueous solutionwhich will occupy about 11 cc per gram or more. By 6 cc per gram, forinstance is meant that each gram of any aluminum phosphate occupied 6 ccin the hydrogel stage. Thus, another way to define the phosphate of thethird technique is that the aluminum salt melt/phosphate mass oraluminum syrup/phosphate mass is sufficiently concentrated so as to givea hydrogel which occupies 3 to 6 cc per gram. The theoretical minimum ifno extraneous water is added is about 3 cc per gram with hydratedaluminum nitrate as the aluminum salt source.

A small amount of a boron compound such as B(OH)₃ can be introduced intothe melt to be cogelled with the aluminum phosphate. Other suitableboron compounds include borates such as ammonium borate. By cogelled asit relates to the boron compound, it is meant that the aluminumphosphate is formed into a true hydrogel in the presence of the boroncompound. It is not known to what extent the boron compound becomesincorporated into the hydrogel structure. The amount of boron compoundpresent when the aluminum phosphate is gelled can vary widely but it isgenerally used in an amount so as to give about 1 to 30 mole percentboron based on the moles of phosphorus.

The neutralization in the first and third techniques of Method A can becarried out either by combining the acid phase (aluminum salt/phosphatesource mixture) with the neutralizing agent or vice versa. One suitablepractice is to drip the acid phase into the neutralizing agent. Thisresults in the production of small spheres or balls of theorthophosphate, particularly with the third technique where the melt ofaluminum salt and source of phosphate ions is dripped or sprayed orotherwise slowly added to a large excess of ammonium hydroxide. Thespheres are subsequently collected, washed, dried and calcined. It isdesirable that the gellation in the first and third methods not occur ata pH of about 4. The pH can be at least 6 during the gel formation.Generally, the pH when the gellation occurs will be 5 to 10, moregenerally 6 to 10. This is effected by slowly combining with stirringabout 72 percent of the neutralizing agent required for completeneutralization and then quickly combining the rest so as to go quicklythrough the 4-5 pH range. Alternatively, about 60 to 70 percent of theneutralizing agent required for complete neutralization can be combinedand the resulting composition allowed to age until gellation occurs.While any base can be used, concentrated ammonium hydroxide, ammonia gasor ammonia dissolved in an alcohol or other non-aqueous solvent arepreferred basic materials. Also ammonium carbonate can be used as theneutralizing agent as can ethylene oxide or propylene oxide.

The aluminum and phosphorus components are selected so as to give anatom ratio of phosphorus to aluminum within the range of 0.2:1 to 1:1,preferably 0.6:1 to 0.9:1. While these compositions can be visualizedfor convenience as a mixture of alumina and aluminum phosphate ofvarying proportions, they are in fact not a mixture.

Method B. The support of Method B is a phosphated silica-containingmaterial generally composed of 80 to 100 weight percent silica, theremainder, if any, being selected from alumina, boria, magnesia, thoria,titania, zirconia, or mixtures thereof. For instance, thesilica-containing material can consist essentially of silica and no morethan 0.2 weight percent of alumina or other metal oxide. This is a lesspreferred embodiment because the presence of the silica lowers theactivity. Other ingredients which do not adversely affect the catalystor which are present to produce some unrelated result can also bepresent. The silica can be a large pore material prepared as describedin U.S. Pat. No. 3,887,494 which issued June 3, 1975 to Dietz coveringthe preparation of silica-titania cogels or U.S. Pat. No. 3,900,457which issued Aug. 19, 1975 to Witt covering the preparation of asynthetic silica, the disclosures of which are hereby incorporated byreference. These types of silicas are known in the art to inherentlygive higher melt flow polymer. However, one of the advantages of the useof the support of Method B is that the silica base which is to bephosphated does not have to be a large pore silica. Thus, less expensivesilicas made by simple tray drying, oven drying or spray drying can beused. These silicas are easier and less expensive to produce and areinherently more durable.

The treatment to produce the phosphated silica support is preferablycarried out simply by forming a slurry of the silica xerogel and asource of phosphate ions, such as orthophosphoric acid by either addingthe acid to the support or the support to the acid. Alternatively, anorthophosphate can be utilized. The preferred phosphate is amonoammonium phosphate although diammonium phosphate or metal phosphatesor any phosphorus compound convertible to a phosphate can be utilized asthe phosphating agent. Any reasonable temperature and atmosphere can beutilized for the incorporation of the phosphorus compound with thesilica with room temperature in air being entirely satisfactory.Alternatively, a phosphorus compound such as POCl₃ (phosphoryl chlorideor PCl₃ phosphorus trichloride) can be vaporized and the vapor contactedwith the silica. These materials will react with surface OH groups andgive off HCl. This vapor treatment can be carried out at thevaporization temperature of the phosphorus compound up to about 400° C.

The term "phosphated" is meant to describe the silica treated with aphosphorus compound as described herein and not necessarily to mean thatphosphate groups are attached to the silica.

Alternatively, the phosphating agent can be added to the silica at thehydrogel stage of the silica.

The phosphorus component is added in an amount to give 0.001 to 0.2,preferably 0.01 to 0.1 gram atoms of phosphorus per mole of silica. Mostpreferably about 1 to 5 mole percent is used which would be about 1 to 5atoms of phosphorus per atom of chromium particularly when the preferred1 weight percent chromium based on the weight of the phosphated supportis used. Generally, the ratio of atoms of phosphorus per atom ofchromium will be in the range of 0.1 to 20, preferably 1 to 10. Based onsurface area, the phosphorus compound is preferably present in an amountsufficient to give about 0.005 to 1, preferably about 0.01 to 0.5 mgP/m² of silica surface as measured by BET nitrogen sorption.

Method C. The support of Method C is a silica/phosphate combination andis also less preferred because the presence of the silica lowers theactivity. The silica/phosphate combination of Method C can be made infour separate techniques. First, the two can be coprecipitated as isknown in the art, for instance as shown in Kirby, U.S. Pat. No.3,342,750 (Sept. 19, 1967), the disclosure of which is herebyincorporated by reference. In accordance with this technique, a silicateis combined with a source of aluminum ions and a source of phosphateions and neutralized to form a hydrogel cogel. The silicate ispreferably a tetrahydrocarbyl orthosilicate, such as ethyl silicate,although sodium silicate can also be used. The aluminum component ispreferably aluminum nitrate although aluminum chloride or other aluminumsalts can be used. The source of phosphate ions is preferablyorthophosphoric acid although monobasic dihydrogen ammonium phosphate,and dibasic hydrogen ammonium phosphate, for instance, can also be used.This reaction is generally carried out in an aqueous medium although apolar organic solvent can be used. A small amount of a boron compoundsuch as boric acid can be introduced into the reaction mixture to becogelled with the aluminum phosphate and silica. Other suitable boroncompounds include borates such as ammonium borate. By cogelled as itrelates to the boron compound, it is meant that the silica/aluminumphosphate is formed into a hydrogel in the presence of the boroncompound. It is not known to what extent the boron compound becomesincorporated into the hydrogel structure. The amount of boron compoundpresent when the silica/aluminum orthophosphate cogel is formed can varywidely but it is generally used in an amount so as to give 0.5 to 15mole percent boron based on the moles of phosphorus.

While any basic material can be used, concentrated ammonium hydroxide,ammonia gas, or ammonia dissolved in alcohol or other nonaqueous solventare preferred basic materials. Ammonium carbonate alone or incombination can be used as the neutralizing agent, as can ethylene oxideor propylene oxide.

The neutralization can be carried out either by adding the acid phase tothe neutralizing agent or vice versa. One suitable practice is to dripor spray or otherwise slowly add the acid phase into the base phase. Itis sometimes preferred that the gellation occur at a pH of at least 5,preferably at least 6. Generally the pH when the gellation occurs willbe in the range of 5 to 10, preferably 6 to 10.

Since gellation will occur spontaneously at a pH of about 4, which isachieved by combining about 72 percent of the base, or otherneutralizing agent, either about 60 to 70 percent of the neutralizingagent is combined slowly and then the composition is allowed to ageuntil gellation occurs, or else about 72 percent of the base is slowlycombined with stirring and then the rest is combined quickly so as to gothrough the 4-5 pH range quickly as described above.

It may be desirable in some instance to coprecipitate other materialssuch as titania with the silica/aluminum orthophosphate cogel or haveother materials present during the gellation.

In accordance with the second technique of Method C, the silica/aluminumorthophosphate cogel is made by impregnating a silica hydrogel orxerogel with aluminum phosphate. This is carried out by combining thesource of aluminum ions and orthophosphate ions with a slurry of silicahydrogel or xerogel and then evaporating the solvent whereupon thealuminum orthophosphate forms. It is believed the aluminumorthophosphate forms to a substantial extent within the pores of thesilica. Alternatively, the source of aluminum and phosphate ions can beadsorbed onto the dry silica. This is largely a physical impregnationand entrapment of the phosphorus component in the pores of the silica.When a silica xerogel is used, instead of evporating to dryness, theevaporation can stop when the liquid in excess of one pore volume isgone but some liquid remains in the pores and a gel formed by adding aneutralizing agent, or an amount of liquid less than one pore volume canbe added initially and the gel formed by adding a neutralizing agent.The scope of the silica can be the same as in Method B.

As to the scope of the aluminum and phosphorus components, the base whenused, and the solvent, is the same as that set out hereinabove withregard to the first technique of Method C. One difference in scopebetween these two techniques is that in this technique a boron compoundsuch as ammonium borate or boric acid can be substituted for thealuminum salt so as to form what is believed to be boron phosphate ontothe silica on evaporating the solvent.

In accordance with the third technique of forming the silica/phosphatebase in accordance with Method C, aluminum orthophosphate is gelled inthe presence of a silica-alumina hydrogel or xerogel. This results informing the silica-alumina as a dispersed phase in an aluminumorthophosphate matrix as opposed to having aluminum orthophosphateimpregnated into the pores of the silica. In accordance with thistechnique, a source of aluminum and phosphate ions is combined with asilica-alumina hydrogel or xerogel and the aluminum orthophosphateformed by combining with a neutralizing agent. The scope of theingredients is the same as in the first technique of Method Chereinabove except monobasic ammonium phosphate is the preferred sourceof phosphate ions. As with the first technique of Method C, a boroncompound can be present during the gellation of the aluminumorthophosphate. Also, the same pH considerations as in the firsttechnique of Method C apply.

In accordance with the fourth technique of Method C for making thephosphate composition, a silica-alumina xerogel and an aluminumorthophosphate xerogel are simply physically mixed. The scope of theingredients for making the separate silica-alumina and aluminumorthophosphate are the same as those used in the first technique ofMethod C for making the cogel. More broadly, any known method of makingsilica-alumina suitable for use as a base in olefin polymerizationcatalysts and any known methods of making aluminum orthophosphate havingrelatively high surface area can be used for producing the silica andaluminum orthophosphate, respectively. In addition, the aluminumorthophosphate can be made by forming a melt of an easily meltedaluminum salt such as hydrated aluminum nitrate, adding a source ofphosphate ions and neutralizing as described in Method A, techniquethree. The resulting silica-alumina and aluminum orthophosphate xerogelscan simply be ground together or blended in a conventional dry blenderor mixed in a slurry with a nonreactive diluent such as a hydrocarbon.In making the phosphate, the same pH considerations apply as in thefirst technique of Method C.

One way of achieving this mixture is to charge the silica-alumina andaluminum orthophosphate in powder form to the activator with thefluidization normally employed during the activation serving to effectthe mixing. Alternatively, the silica-alumina and aluminumorthophosphate can be separately activated, the divalent chromium addedand thereafter the two combined.

The aluminum and phosphorus components in Method C are selected so as togive an atom ratio of phosphorus to aluminum within the range of 0.2:1to 1:1, preferably 0.6:1 to 0.9:1. Further with respect to the relativeproportions, in all techniques except technique two, the silica andphosphate will generally be used in molar ratios of 10:1 to 1:20 molesof silica per mole of phosphate (or gram atoms of phosphorus),preferably 2:1 to 1:2 moles per mole or gram atom. In embodiment two,the phosphate will generally be used in an amount within the range of 1to 50, preferably 5 to 25 mole percent based on the moles of silica.

Method D. In accordance with Method D for preparing thephosphate-containing base, alumina is phosphated in a manner analogousto the phosphating of silica in Method B. As with the silica, thealumina can be phosphated either by combining the phosphating agent withthe hydrogel or combining the phosphating agent with the xerogel. Thesame scope of phosphating agents applicable to phosphating the silicaare applicable to phosphating the alumina. In addition to phosphatingpure alumina, it is also within the scope of this method of producingthe phosphate-containing base to utilize an aluminum phosphate describedin Method A having a low (less than about 0.6, generally less than 0.4)phosphorus to aluminum ratio and treating it with the phosphating agentto impart additional phosphate to the surface. The alumina can containminor amounts of other ingredients which do not affect the quality ofthe final catalyst, but is generally essentially pure alumina or lowphosphorus aluminum phosphate.

If an alumina hydrogel is phosphated, the phosphoric acid is preferablyincorporated in the organic water miscible liquid used to wash thehydrogel. More specifically, the hydrogel may be washed with water, thenwith an organic liquid such as isoamyl alcohol containing phosphoricacid, then filtered and the solvent allowed to evaporate.

Whether the starting material is pure alumina or a low phosphorusaluminum orthophosphate, Method D takes advantage of the fact that someproperties, such as surface area, are favored by high aluminum contentwhereas others, such as melt index potential, are favored by highphosphate content. By imparting a phosphate layer on the surface of purealumina or low phosphorus aluminum phosphate, both trends can be takenadvantage of.

The phosphating agent is preferably used in an amount to react with thealumina surface and give a P/Al ratio of this reaction product on thesurface of 0.2:1 to 1:1, preferably 0.6:1 to 0.9:1. In practice,however, it is possible to use as much phosphating agent as desired withthe excess simply being washed off after the phosphating treatment iscomplete. Overall the P to Al ratio will be less than 0.3:1, generally0.1:1 to 0.3:1, preferably 0.1:1 to 0.2:1. Ratios as low as 0.05:1overall have been found to be satisfactory. The phosphating treatment isgenerally carried out at a temperature of 15° C. to 500° C., preferablyroom temperature to the boiling point of the solvent if a phosphatesolution is used or 500° C. if a vapor is used and a time of 1 minute to2 hours, preferably 2 minutes to 30 minutes. The phosphated aluminaresults in a catalyst which surprisingly gives a bimodal molecularweight distribution in ethylene polymerization.

In any of the four methods set out hereinabove, wherein a hydrogel isformed, it is greatly preferred that the water be removed to convert thehydrogel to a xerogel by means of azeotropic distillation or washingwith a water miscible liquid. Any such water miscible liquid effectivein aiding in removing water can be utilized. Generally, such liquids arerelatively volatile, oxygen-containing organic compounds havingrelatively low surface tension. Exemplary classes of such compounds arealcohols, ketones, and esters. Particularly suitable are alcohols, suchas isoamyl alcohol and esters, such as ethyl acetate.

As to Method A, it is readily apparent that the hydrogel resulting fromtechnique 1 utilizing an aqueous solution of the aluminum component, thephosphorus component, and an aqueous solution of the base results infree water in the hydrogel. In technique 2 of Method A, there could besome water from the water in the phosphoric acid although there is nowater from a base since a base is not required and hence this isessentially an anhydrous preparation. In technique 3 of Method A, thereis essentially no free water in the resulting gel from the acid phaseingredients so that the resulting gel inherently has the goodcharacteristics associated with the hydrogels made in non-aqueoussystems. However, there may be some water carried over from water ofhydration of the aluminum component and/or from the base and also it maybe desirable in some instances in technique 3 of Method A to wash theresulting gel with water in which case azeotropic distillation to removethe water is desirable.

In Method C, techniques 1 and 3, carried out utilizing aqueous solutionsof the ingredients involve the formation of hydrogel having excess freewater and thus create the situations where azeotropic distillation orwashing with a water miscible solvent is highly desirable.

Regardless of which of the four methods (A, B, C, or D) describedhereinabove are used, the resulting support is calcined or activated andthereafter combined with the chromium component. Throughout thisdescription the phosphate component has been referred to as the supportor base. The phosphate component and the chromium component can becombined by adding each as a separate stream to the reactor or thechromium component can be impregnated onto the phosphate component priorto being added to the reactor. In this case, the chromium component isadded in an anhydrous fashion. Thus briefly, the technique for formingthe catalyst involves forming a phosphate-containing support, activatingthe support by heating in a reducing, inert or oxidizing ambient, andadding divalent chromium anhydrously to form a catalyst (or adding eachseparately to the reactor).

Since neither the chromium component or the phosphate component is aneffective catalyst by itself, the phosphate can be viewed as a supporteven when the two are added to the reactor as separate streams. Becauseof the possibility of contamination of the impregnated and driedphosphate with water and/or air, which lowers activity, it is actuallypreferred to introduce the support and the chromium component asseparate streams into the reaction zone.

In some instances, the catalyst is used with a cocatalyst, such as anorganoaluminum compound to increase activity. Other ingredients which donot adversely affect the catalyst can be used with the final catalystsuch as other cocatalysts or antistatic agents in the polymerizationzone, for instance.

The term "xerogel" is used to refer to the gel resulting from theremoval of free water from the hydrogel.

The activation of the xerogel can be carried out at temperatures knownin the art although the phosphate-containing base of this invention canbe activated at slightly lower temperatures, for instance temperaturesof 150°-800° C., preferably 400°-750° C., compared with the 450°-1000°C. temperature generally employed for silica bases. The ideal activationtemperature can be seen from FIG. 1. With technique 4 of Method C, ifthe silica-alumina and aluminum phosphate are to be combined afteractivation, each can be activated at the temperature optimum for thatcomponent, i.e., 450°-1000° C. for the silica-alumina and 150°-800° C.for the phosphate. Thus broadly temperatures of 150°-1000° C. can beused. Suitable activation times are from 1 minute to 48 hours,preferably 0.5 to 10 hours.

When the activating ambient is an oxidizing ambient, it can be anyoxidizing ambient but for convenience and economy, an oxygen-containingambient such as air is preferred. Preferred reducing ambients are pureCO and CO/N₂ mixtures. Preferred inert ambients are N₂ and vacuum. Airis preferred simply because of cost.

The term "bis-(cyclopentadienyl)chromium(II) compound" includes not onlybis-(cyclopentadienyl)chromium(II) but substituted derivatives thereofin which the cyclopentadienyl rings contain one or more substituentswhich do not affect the ability of the adsorbed substitutedbis-(cyclopentadienyl)chromium(II) compound to function as an ethylenepolymerization catalyst. The specific bis-(cyclopentadienyl)chromium(II)compound, bis-(cyclopentadienyl)chromium(II) sometimes called chromocenehas the following postulated structure: ##STR1##

Also suitable is bis-(fluoroenyl)chromium(II) ##STR2## andbis-(indenyl)chromium(II), ##STR3## as well asbis-(cyclopentadienyl)chromium(II) compounds having substituted ligandsof the formula ##STR4## where one or both R groups are selected from 1-6carbon atom alkyl radicals. These materials can be thought of as adivalent cation (chromium) coordinated by two negatively chargedcyclopentadienyl ligands.

The bis-(cyclopentadienyl)chromium(II) compounds are solids soluble inmany organic solvents. Preferred solvents are non-polar liquids atambient temperatures. Types of suitable solvents include alkanes,cycloalkanes, alkenes, and aromatic hydrocarbons. Exemplary solventsinclude pentane, n-hexane, decane, cyclohexane, methylcyclohexane,1-butene, benzene, xylenes, and mixtures of one or more of the purecompounds. Preferably, a sufficient quantity of a solution of thechromium component is used to completely wet the support and fill theporous structure to insure even distribution of the metal compound onthe support. Generally, the solutions contain from about 0.002 to about25 weight percent of the organochromium compound whether used toimpregnate the support or added separately.

A sufficient volume of the solution of the organochromium compound istaken so as to provide from .01 to 10, preferably 0.1 to 5, morepreferably about 1-3 weight percent chromium based on the weight of theactivated support. The contact between the support and organochromiumsolution is effected in a conventional way such as by slurrying and atany convenient temperature. Generally, ambient temperature is used,although temperatures ranging from about the freezing point of thesolvent to as high as about 300° F. can be employed during thecontacting period. Contact times from a few seconds to several hours areadequate. The same amounts are used when the chromium component is addedas a separate stream. This is slightly more chromium than is typicallyused in the prior art.

The incorporation of the chromium component onto the activated base ispreferably carried out in an inert atmosphere, such as nitrogen or undera vacuum, and the resulting catalyst is maintained in an inertatmosphere or under vacuum until it is used.

The cocatalyst, when used, is an organometal compound, preferably atrihydrocarbylborane, more preferably trialkylborane, the alkyl groupspreferably having 1 to 12, more preferably 2 to 5, carbon atoms pergroup. Triethylborane, tri-n-propylborane, and tri-n-butylborane aresuitable for instance. Less preferred but also suitable are aluminumcompounds of the formula AlR'_(n) X_(3-n) where X is a hydride orhalide, R' is a 1 to 12 carbon atom hydrocarbyl radical and n is aninteger of 1 to 3. It is believed the cocatalyst simply acts as ascavenger for catalyst poisons. The term "metal" in organometal isintended to include boron.

The cocatalyst when used is utilized in an amount so as to give an atomratio of metal to chromium within the range of 0.5:1 to 10:1, preferably2:1 to 5:1. Based on the solvent if any in the polymerization zone, theamount of metal compound cocatalyst is generally within the range of 0.5to 20, preferably 2 to 10 parts by weight per million parts by weight ofthe solvent, these amounts being based on the total reactor contents ininstances where no solvent is utilized. The cocatalyst can either bepremixed with the catalyst or added as a separate stream to thepolymerization zone, the latter being preferred.

The support of this invention can be further treated in the same manneras conventional silica catalysts are sometimes given special treatments,such as being fluorided or being reduced and reoxidized as disclosed inMcDaniel et al, U.S. Pat. No. 4,151,122 (Apr. 24, 1979), the disclosureof which is hereby incorporated by reference. Fluoriding the supporttends to produce a catalyst which gives higher molecular weight polymer.The support can also have chromium on it prior to combination with thedivalent chromium. Generally the chromium in such cases will behexavalent chromium as a result of the chromium being present during acalcining step but zerovalent chromium could be introduced onto thesupport and/or added as a separate stream to the reactor in addition tothe divalent chromium.

The catalysts of this invention can be used to polymerize at least onemono-1-olefin containing 2 to 8 carbon atoms per molecule. Suchcatalysts are of particular applicability in producing ethylenehomopolymers and copolymers of ethylene and one or more comonomersselected from 1-olefins containing 3 to 8 carbon atoms per molecule suchas propylene, 1-butene, 1-pentene, 1-hexene and 1-octene. These polymerscan be produced by solution polymerization, slurry polymerization, andgas phase polymerization using conventional equipment and contactingprocesses. Contacting of the monomer of monomers with the catalyst canbe effected by any manner known in the art of solid catalyst. Oneconvenient method is to suspend the catalyst in an organic medium and toagitate the mixture to maintain the catalyst in suspension throughoutthe polymerization process.

The catalyst of this invention is particularly suitable for use inslurry polymerization systems to produce a complete spectrum of polymersso far as melt flow is concerned, utilizing a single catalyst.Everything from ultra high molecular weight to resins which may have amelt index of as little as 0 (weight average molecular weight of as muchas four million, more generally three to three and one-half million) topaper coating and injection molding grade resins which may require amelt index of 20 or greater can be produced from a single catalystsystem simply by the use of a molecular weight control agent, such ashydrogen. While hydrogen is known as a molecular weight control agent,the phosphate-containing supported catalyst of this invention displaysan unusual sensitivity to hydrogen so that by controlling the amount ofhydrogen utilized, polymers having a very high molecular weight asindicated by low melt flow, through polymers having a very low molecularweight as indicated by high melt flow can be obtained.

Surprisingly, changes in reactor temperature do not have the unusualeffect of varying melt flow nor do changes in activation temperaturehave the usual effect of varying melt flow (of course activity isaffected by changes in activation temperature). Thus, polymers having abroad spectrum of molecular weight can be produced using a singlecatalyst utilizing whatever activation temperature and reactortemperature are needed for good activity.

With slurry polymerization of ethylene and predominantly ethylenecopolymer systems, the feasible temperature range is generally about200°-230° F. (93°-110° C.) and the commercial systems are generally runas close to the maximum as possible, i.e., 225° F.±5° F. (107° C.±3° C.)in order to get the highest possible melt index. The catalyst of thisinvention easily allows running at the low end of the possibletemperature range, i.e., 205° F.±5° F. (96° C.±3° C.) in systemsnormally employing 225° F. (107° C.). Even temperatures below 205° F.(96° C.) can be used including temperatures of 190° F. to 205° F. (88°C. to 96° C.) and even below 190° F. (88° C.) without reactor fouling.The lower temperature gives a relatively higher monomer partialpressure, thus giving higher activity.

Productivities in the range of 5,000 to 10,000 gm/gm catalyst/hour areobtained with the catalyst systems of this invention.

Catalysts of this invention have the further advantage of not having anymeasurable induction time between initial contact with the monomer andthe initiation of polymerization. As can be seen from FIG. 2 there is afundamental difference between zerovalent chromium and thebis-(cyclopentadienyl)chromium(II) compounds of this system, each on aphosphate base in that the catalysts of the invention very quickly reacha high productivity level. Thus, while both the zerovalent chromiumsystems and the divalent chromium systems of this invention differ fromthe chromium oxide on silica in not having an induction period, thecatalysts of the invention offer the further advantage of very quicklyreaching a high rate of polymer production and hence are ideally suitedfor use in a polymerization process employing a short residence time.For instance an average residence time of 5 to 40 minutes or even 10 to30 can be used.

When hydrogen is used in the prior art, it is generally used at partialpressures up to 120 psia (0.8 MPa), preferably within the range of 20 to70 psia (0.01 to 0.48 MPa). These same amounts of hydrogen can also beused in this invention, although because of the high sensitivity tohydrogen, it may be preferred in the present invention to use 5 to 20psia.

The tendency of the catalysts of this invention to produce higher meltflow polymers when hydrogen is utilized corresponds to the tendency ofother catalyst systems to produce higher melt flow polymers whenhydrogen is utilized, the difference being that the catalyst of thisinvention is unusually sensitive to the effects of hydrogen in loweringmolecular weight and in the absence of hydrogen unusually high molecularweight polymer is produced thus giving an extraordinarily broad spectrumof polymers, so far as melt flow is concerned, from a single catalyst.

If the object is to produce a copolymer, 0.5 to 20 mole percentcomonomer or more can be used, although enough to give 0.2 to 3 molepercent incorporation is preferred. As used herein, the term "at leastpredominantly ethylene" means an essentially pure ethylene monomer feedas a feed containing ethylene as the principal monomer with 0.5 to 20mole percent comonomer.

In this regard, it must be kept in mind that HLMI/MI ratios (shearresponse) are meaningful only if compared on a comparable melt indexbasis. The references herein to melt index (MI) refer to ASTM D1238-65T, Condition E, and to high load melt index (HLMI) refer to ASTMD 1238-65T, Condition F, the difference being 21,600 gram weight in thehigh load test and 2,160 gram weight in the regular melt index test, thetemperature being 190° C. in each instance when the tests are utilizedfor predominantly ethylene polymers and copolymers.

Whether determined by shear response or the newer RDI (RheometricDynamic Spectrophotometer index) test, the molecular weight distributionas expressed by M_(w) /M_(n) wherein M_(w) is the weight averagemolecular weight and M_(n) is the number average molecular weight, isless than anything previously attainable in the prior art with achromium catalyst.

Further, as can be seen from the size exclusion chromatography (SEC)curves of FIG. 3, increasing hydrogen pressure not only increases meltflow (reduces molecular weight) but also shifts the distribution curveso that the distribution stays narrow. Actually it gets even more narrowsince there is an ultra-high molecular weight fraction in the samplerepresented by the upper curve which does not go into solution and henceis not shown.

Another instance in which the catalysts of this invention give an effectwhich is opposite to that obtained with chromium catalysts of the priorart is that the resulting polymers exhibit little or no vinylunsaturation.

In the following examples, productivity is the grams of polymer producedper gram of catalyst for the time of the run and activity is the gramsof polymer produced per gram of catalyst per hour. Yield simply meansthe actual weight of polymer produced.

EXAMPLE I

Commercial grade solvents were distilled from an appropriate dryingagent and stored under argon prior to use. Anhydrous chromocene waspurchased from Strem Chemical Company. Unless specified otherwise, allmanipulations were carried out under an inert atmosphere. The bis-arenechromium compounds Cr(Tol)₂ (ditoluene chromium) and Cr(Mes)₂(dimesitylene chromium) were made according to literature methods. Thecompound Cr(Cum)₂ (dicumene chromium) was purchased from the AldrichChemical Company.

The aluminum phosphate used in the following experiments was madeaccording to a procedure in which a melt of aluminum nitrate andmonobasic ammonium phosphate were gradually neutralized withconcentrated ammonia. After washing the resulting gel with water andthen acetone, it was then dried at 70° C. in a vacuum oven. Activationat the appropriate temperature was carried out in a stream of dry oxygenfor three hours. It was then allowed to cool in an argon stream andfinally stored under an argon or nitrogen atmosphere. The P:Al atomratio was 0.8.

All polymerization runs were carried out in a two liter bench reactorunder slurry (particle form) conditions. The diluent was isobutane andthe reactor temperature was 96° C. unless specified otherwise. Reactorpressure held at 550 psig during the polymerization with ethylene beingfed on demand.

The actual charging of the reactor was accomplished by either of thefollowing methods.

Method A: Separate streams of support and chromium solution.

After purging the reactor at 100° C. with a stream of nitrogen for atleast 15 minutes, the system was flushed several times with isobutane. Apreweighed amount of support was charged against a slight countercurrentof gaseous isobutane. Approximately 500 mL of liquid isobutane was thenadded to the reactor. The appropriate amount of the organochromiumsolution was added to the inject port and flushed into the reactor withthe remaining charge of isobutane. When desired, hydrogen was then addedand finally the reactor pressurized with ethylene.

Method B: Impregnation of support with organochromium solution.

A preweighed sample of support was slurried in a hydrocarbon such aspentane. The amount of organochromium solution was then added to givethe desired Cr:support ratio, and the slurry shaken until completediscoloration of the supernatant was observed. Excess solvent was thendecanted and the catalyst dried under vacuum at 50° C. Following thepurging procedure outlined in Method A, a preweighed portion of thecatalyst was charged to the reactor as a free flowing powder. The totalcharge of isobutane was then added, followed by the appropriate amountof hydrogen and finally ethylene.

The rheological data was obtained using a Rheometrics DynamicSpectrometer (RDS). The polymer sample was first compression molded intoslabs. A circular disk with 1/8" thickness and 1" diameter was then cutfrom the slab and mounted between the concentric oscillating disks ofthe spectrometer. While holding the temperature constant at 190° C., theinstrument measures the in phase (storage modulus, G') and the out ofphase (loss modulus, G") components of the strain induced by the shearstress of the oscillating plates as a function of the oscillationfrequency, ω. The melt viscosity was also determined as a function of ω.

The average activity for the invention catalysts under optimumconditions was approximately 7-8000 g/g AlPO₄ /hr whereas the averagefor bis-arene chromium/AlPO₄ systems was around 2-3000 g/g AlPO₄ /hr.Table 1 gives the specific polymerization data for a variety of runs forthe invention and zerovalent systems. All of the runs in Tables I, II,III and IV were made according to Method A in which an amount of AlPO₄support (0.02-22 g) was charged to the reactor followed by a givenvolume (1-3 mL) of the organochromium solution (˜0.015M in n-pentane).

                  TABLE I                                                         ______________________________________                                        POLYMERIZATION DATA F0R THE (Cp).sub.2 Cr/AlPO.sub.4.sup.a                    AND Cr(Mes).sub.2 /AlPO.sub.4.sup.b CATALYSTS                                        Chromium  Wt. %   Activity Activity                                                                             ppm                                  Run    Compound  Cr.sup.c                                                                              g/gAlPO.sub.4 hr                                                                       g/gCr/hr                                                                             Cr.sup.d                             ______________________________________                                        1      (Cp).sub.2 Cr                                                                           1.5     7000     457,000                                                                              2.2                                  2      (Cp).sub.2 Cr                                                                           2.8     7200     258,000                                                                              3.9                                  3      (Cp).sub.2 Cr                                                                           1.1     5100     463,000                                                                              2.2                                  4      (Cp).sub.2 Cr                                                                           0.6     2700     450,000                                                                              2.2                                  5      (Cp).sub.2 Cr                                                                           3.1     2200      73,000                                                                              13.6                                 6      (Cp).sub.2 Cr                                                                           0.3     1300     458,000                                                                              2.2                                  Control 1                                                                            Cr(Mes).sub.2                                                                           3.0     1670      56,000                                                                              17.8                                 Control 2                                                                            Cr(Mes).sub.2                                                                           1.5     2580     169,000                                                                              5.9                                  Control 3                                                                            Cr(Mes).sub.2                                                                           1.3     2430     194,000                                                                              5.2                                  Control 4                                                                            Cr(Mes).sub.2                                                                           0.5     1780     374,000                                                                              2.7                                  Control 5                                                                            Cr(Mes).sub.2                                                                           0.7     2110     317,000                                                                              3.2                                  Control 6                                                                            Cr(Mes).sub.2                                                                           2.9     2580      89,000                                                                              11.2                                 Control 7                                                                            Cr(Mes).sub.2                                                                           7.1      390      6,000 166.7                                ______________________________________                                         .sup.a Bis(cyclopentadienyl)chromium(II) on AlPO.sub.4 support activated      at 600° C.                                                             .sup.b Dimesitylene chromium (i.e. zerovalent) on AlPO.sub.4 support          activated at 600° C.                                                   .sup.c Weight percent of chromium charged to the reactor based on the         weight of the aluminum phosphate charge. All runs on this table used          Method A.                                                                     .sup.d Parts per million chromium in the polymer based on total Cr charge     These data show higher productivities for the                                 bis(cyclopentadienyl)chromium(II) compound as compared with zerovalent        chromium based on similar weights of chromium present.                   

                                      TABLE II                                    __________________________________________________________________________    POLYMERIZATION AND RHEOLOGICAL DATA                                                     Act.                  Activity                                                                           Melt  Solution                                     Temp.     H.sub.2                                                                              Shear                                                                              (gm/ Viscosity                                                                           Viscosity                          Run   Support                                                                           °C.                                                                        Chromium                                                                            (Psig)                                                                           HLMI                                                                              Response                                                                           gm/hr)                                                                             (M Poise)                                                                           Dl/g Est. MW                       __________________________________________________________________________     7    AlPO.sub.4                                                                        600 (Cp).sub.2 Cr                                                                       0  0        6,700                                                                              --    15.34                                                                              3,000,000                      8    AlPO.sub.4                                                                        800 (Cp).sub.2 Cr                                                                       0  0        7,200                                                                              96.2  17.07                                                                              3,500,000                      9    AlPO.sub.4                                                                        650 (Cp).sub.2 Cr                                                                       0  0        6,700                                                                              106.0 Inso.                                                                              ≧4,000,000.sup.(a)                                                     1                             10    AlPO.sub.4                                                                        600 (Cp).sub.2 Cr                                                                       2  .05      3,000                                                                              14.2  6.57 1,000,000                     11    AlPO.sub.4                                                                        600 (Cp).sub.2 Cr                                                                       3  .15      3,000                                                                              10.5  5.40   800,000                     12    AlPO.sub.4                                                                        600 (Cp).sub.2 Cr                                                                       5  1.24     11,200                                                                              1.0  3.43   407,000                     13    AlPO.sub.4                                                                        600 (Cp).sub.2 Cr                                                                       10 6.38     4,600                                                                              --    3.29   385,000                     14    AlPO.sub.4                                                                        600 (Cp).sub.2 Cr                                                                       15 11.75    4,400                                                                              --    2.20    220,000                    Control 8                                                                           AlPO.sub.4                                                                        600 Cr(Tol).sub.2.sup.(b)                                                               0  .28      2,100                                                                              --    Insol.                                                                             ≧4,000,000.sup.(a)                                                     3                             Control 9                                                                           AlPO.sub.4                                                                        600 Cr(Mes).sub.2                                                                       0  .36      3,000                                                                              --    Insol.                                                                             ≧4,000,000.sup.(a)                                                     .                             Control 10                                                                          AlPO.sub.4                                                                        600 Cr(Mes).sub.2                                                                       1  72.95    2,300                                                                              --    2.45   255,000                     Control 11                                                                          Silica                                                                            600 (Cp).sub.2 Cr                                                                       0           1,042                                         Control 12                                                                          Silica                                                                            600 (Cp).sub.2 Cr                                                                       0           1,535                                         Control 13                                                                          Silica                                                                            600 (Cp).sub.2 Cr                                                                       0           1,900                                         Control 14                                                                          Silica                                                                            600 (Cp).sub.2 Cr                                                                       3  1.34                                                                              67   1,634                                         Control 15                                                                          Silica                                                                            600 (Cp).sub.2 Cr                                                                       5  5.38                                                                              77   1,136                                         Control 16                                                                          Silica                                                                            600 (Cp).sub.2 Cr                                                                       10 32.2                                                                              53     138                                         __________________________________________________________________________     .sup.(a) Polymers insoluble in trichlorobenzene (TCB) are assumed to have     molecular weight ≧4,000,000.                                           .sup.(b) Ditoluene chromium.                                             

These data show the ability to produce zero melt flow polymer using theinvention catalyst. As can further be seen the molecular weight isconsiderably higher than for a commercial ultra high molecular weightpolymer, Hostalen GUR (American Hoechst) having a molecular weight ofabout 2,500,000.

As can be seen from Control Runs 11-16, the productivities forchromocene with silica added separately are much lower (138 to 1,900)compared with 3,000 to 11,200 for chromocene on phosphate (invention).In addition, the shear is much higher (53-77) for inventive runscompared with 22-29 (Table III). Zerovalent chromium and silica addedseparately is inactive.

Blanks indicate no data are available or that none can be obtained.

                  TABLE III                                                       ______________________________________                                        MOLECULAR WEIGHT DISTRIBUTION DATA                                            Run     Compound  H.sub.2 Psig                                                                           MI   Shear Response                                                                          HI.sup.a                            ______________________________________                                        Control 11                                                                            Cr(Mes).sub.2                                                                           1        .05  1590      77.8                                Control 12                                                                            Cr(Mes).sub.2                                                                           3        .49  350       --.sup.b                            Control 13                                                                            Cr(Mes).sub.2                                                                           5        .70  521       41.8                                Control 14                                                                            Cr(Mes).sub.2                                                                           10       4.50 196       30.0                                Control 15                                                                            Cr(Tol).sub.2                                                                           1        .02  413       --                                  Control 16                                                                            Cr(Tol).sub.2                                                                           3        .36  257       --                                  Control 17                                                                            Cr(Tol).sub.2                                                                           5        1.18 196       --                                  15      (Cp).sub.2 Cr                                                                           5        .09  22        4.3                                 16      (Cp).sub.2 Cr                                                                           10       .22  29        6.3                                 17      (Cp).sub.2 Cr                                                                           15       .51  23        5.0                                 18      (Cp).sub.2 Cr                                                                           20       5.57 22        3.3                                 19      (Cp).sub.2 Cr                                                                           25       16.31                                                                              24        3.6                                 ______________________________________                                         .sup.a Heterogeneity index, M.sub.w /M.sub.n, as determined from size         exclusion chromatography.                                                     .sup.b A dash signifies not determined.                                  

These data show very narrow molecular weight polymer is produced withthe invention catalyst. (Shear response of 22-29). Such narrow molecularweight distribution is unusual although not previously unknown. Ethylenepolymer with a distribution below 25 may be unknown in prior artethylene polymer. In any event, as is shown in Example VIII hereinafter,polymer made with the chromium(II) compounds on a phosphate-containingsupport exhibit a very high degree of methyl branching. Polymers of amolecular weight distribution no more than 29 and at least 0.4 molepercent methyl branching were heretofore unknown.

                  TABLE IV                                                        ______________________________________                                        RHEOLOGICAL DATA BY RDS ANALYSIS                                                                         H.sub.2                                                                             Viscosity.sup.a                              Run    Compound  Support   (Psig)                                                                              M Poise Tan δ.sup.a                    ______________________________________                                        20     (Cp).sub.2 Cr                                                                           F--AlPO.sub.4.sup.b                                                                      0    106.0   0.15                                 21     (Cp).sub.2 Cr                                                                           AlPO.sub.4                                                                               0    96.2    0.13                                 22     (Cp).sub.2 Cr                                                                           AlPO.sub.4                                                                              20    14.2    1.47                                 23     (Cp).sub.2 Cr                                                                           AlPO.sub.4                                                                              30    10.5    0.73                                 24     (Cp).sub.2 Cr                                                                           AlPO.sub.4                                                                              50    1.0     3.00                                 Control                                                                              Cr(Cum).sub.2.sup.c                                                                     AlPO.sub.4                                                                               0    24.1    0.27                                 12                                                                            Control                          39.1    0.30                                 13                                                                            ______________________________________                                         .sup.a All values measured at 0.1 Radians/Sec., 190° C.                .sup.b Fluorided AlPO.sub.4.                                                  .sup.c Dicumene chromium.                                                

These data show the ability of the invention catalyst to inherentlyproduce a high viscosity polymer, but because of sensitivity tohydrogen, the same catalyst can produce a complete spectrum of polymersso far as viscosity or melt flow is concerned.

EXAMPLE II

In this example, AlPO₄ produced as in Example I and having a P:Al atomratio of 0.8 was calcined at 700° C. It was impregnated (Method B) withbis-(cyclopentadienyl)chromium(II) and used with and without TEB withthe following results.

    ______________________________________                                        TEB        Time, Minutes                                                                             Producitivity, g/g                                     ______________________________________                                        0          40          1440                                                   8 ppm      75          3440                                                   ______________________________________                                    

As can be seen, the cocatalyst increased the productivity considerably.While the triethylborane (TEB) run was carried out for 75 minutescompared with 40 for the run with no TEB, as can be seen from FIG. 2,little additional polymer would be formed after 40 minutes and thus thisis a valid comparison.

EXAMPLE III

In this example, several conventional aluminum phosphates were made asdescribed in Hill et al, U.S. Pat. No. 4,219,444 (Aug. 26, 1980). Onealuminum phosphate, having a 0.8 P/Al atom ratio, was prepared bydissolving 93.8 g (0.25 mole) of Al(No₃)₃. 9H₂ O and 23 g (0.20 mole) ofNH₄ H₂ PO₄ in 2.5 L of deionized water. To the stirred solution wasadded 40 mL of concentrated ammonium hydroxide solution (28%) to bringthe pH of the mixture to about 6. The precipitate was filtered off,dried overnight in a vacuum oven at 80° C. and the dry product wasactivated by calcination for 3 hours at 600° C. as described in ExampleI.

Ethylene was polymerized in Run 1 as in Method A of Example I bycharging the reactor with 0.1726 g of the activated aluminum phosphateand 2 mL of the bis-(cyclopentadienyl) chromium(II) solution employed inRuns 1-6 of Table I. The calculated amount of chromium employed, basedon the aluminum phosphate charge, was 2.3 weight percent. In the absenceof hydrogen, a reactor pressure of 550 psig and a reactor temperature of91° C., 300 g of polyethylene was produced in one hour. The calculatedactivities were 1740 g polymer per g AlPO₄ per hour and 75,000 g polymerper g chromium per hour.

As can be seen, in comparing the control catalyst used in Run 1 withinvention catalysts of Runs 1, 2, 3 of Example I, which bracket theamount of chromium employed in this Example, the control catalyst ismuch less active. The invention catalysts show activities based on AlPO₄charged ranging from 5100 to 7200 g polymer per g AlPO₄ per hour whereason the same basis the control catalyst shows 1740 g polymer per g AlPO₄per hour.

It should be noted that the control catalyst was used at a reactortemperature of 91° C. while the invention catalysts were used at areactor temperature of 96° C. in the polymerization runs. In slurrypolymerization, at the same total reactor pressure that was used, theeffective ethylene pressure increases with decreasing reactortemperature. Consequently, if the control catalyst was used at 96° C.,the productivity figures noted above at 91° C. would be somewhat lower.

EXAMPLE IV

This example shows the difference in microstructure as determined frominfrared spectra between polymer made using the invention catalyst and azerovalent catalyst.

    ______________________________________                                                  Groups/1000 Carbon Atoms                                            Run   Chromium  MI         Vinyl Methyl                                                                              Additive                               ______________________________________                                        1     (Cp).sub.2 Cr                                                                           0      HLMI  0.1   2.5   None                                 2     (Cp).sub.2 Cr                                                                           0      HLMI  0.1   1.7   TEB                                  3     (Cp).sub.2 Cr                                                                           3000         0     10.8  H.sub.2                              4     Cr(Cum).sub.2                                                                           15     HLMI  5.2   6.0   None                                 5     Cr(Cum).sub.2                                                                           163          7.8   9.0   H.sub.2                              6     Cr(Cum).sub.2                                                                           0.14         4.8   6.1   TEB                                  ______________________________________                                    

EXAMPLE V

This example shows the effect of combining abis-(cyclopentadienyl)chromium(II) compound with an aluminum phosphatebase already having hexavalent chromium on it. Cr/AlPO₄ (P/Al=0.8)produced by cogelling aluminum phosphate and chromium nitrate to give11/2 weight percent chromium based on the weight of AlPO₄ was calcinedat 600° C. and was charged to the reactor (between 0.04-0.1 gm) alongwith 1 mL of chromocene solution and 12 ppm of TEB. Run at 102° C., 550psig ethylene. (No H₂ used.) The results were as follows:

    __________________________________________________________________________    Run                                                                              Chromocene                                                                             Prod., g/g                                                                          MI HLMI                                                                              HLMI/MI                                                                             Den..sup.a                                                                        Flex..sup.b                                                                       ESCR.sup.c                             __________________________________________________________________________    1  0.011                                                                             g Cr/mL                                                                            944/41 min.                                                                         0  0   --    0.9275                                                                             628                                                                              ≧1000                           2  0.011                                                                             g Cr/mL                                                                            2686/hr                                                                             0  .09 --    0.9527                                                                            1360                                                                              ≧1000                           3  0.0011                                                                            g Cr/mL                                                                            2400/hr                                                                             .08                                                                              26  325   0.9679                                                                            1693                                                                                100                                  __________________________________________________________________________     .sup.a density, g/cm.sup.3 ; ASTM D 150568.                                   .sup.b flexural modulus, MPa; ASTM D 79066.                                   .sup.c environmental stress cracking resistance, F.sub.50 hours; ASTM D       169370.                                                                       1. These runs compared with Runs 7 and 8 of Table II where chromocene was     used without TEB show that:                                                   In the absence of TEB or H.sub.2, MI = HLMI = 0 was always obtained.          Whereas in above runs when TEB/Cr ratio is high, a measurable MI or HLMI      resulted.                                                                     2. These runs compared with Runs 16-19 of Table III show that the MWD is      narrow in Runs 16-19 whereas TEB and the two types of chromium give broad     MWD.                                                                           3. The density is higher in Runs 1 and 2 above giving excellent              stiffness.                                                                    4. The ESCR/Flex. combination is very good in the above runs.            

EXAMPLE VI

This example shows that with other chromium catalysts which areeffective when added to a phosphate base and calcined, are not effectivewhen added as a separate stream to the reactor. T-butyl chromate wasadded to a reactor as a separate stream with AlPO₄. The aluminumphosphate had a P/Al ratio of 0.8 and was calcined at 700° C. Thepolymerization was carried out at 96° C. with 550 psig ethylene.Separate streams, one comprising 0.2477 gm AlPO₄ and the other 1/4 mLt-butyl chromate solution in hexane were added (0.01 gm Cr/mL) (i.e. 1%Cr calculated). Eight ppm TEB was used. The run was dead.

EXAMPLE VII

The following example is presented to show miscellaneous combinationspossible utilizing the catalyst system of this invention and contrastthe various systems with divalent π-bonded chromium on silica. Thealuminum phosphate was prepared as in Example I and the polymerizationwas carried out as in Example I. The results were as follows:

                                      TABLE VI                                    __________________________________________________________________________              Act..sup.(1)                                                        Run                                                                              Base   Temp., °C.                                                                   Cr(Cp).sub.2,.sup.(4) mL                                                              Add.   Prod., g/g                                                                          Time                                                                             MI    HLMI                                                                             Flex.                                                                            Den.                                                                             ESCR                                                                              HI.sup.(5)         __________________________________________________________________________    1  AlPO.sub.4                                                                           600   1/2     None   1,700 50 0  HL --   585                                                                            0.9220                    2  AlPO.sub.4                                                                           600   1/2      4 ppm TEB                                                                           3,083 40 0  HL --                              3  AlPO.sub.4 /Cr.sup.+6                                                                .sup. .sup. 250.sup.(2)                                                             1        4 ppm TEB                                                                           1,300 30 0  HL --   575                                                                            0.9262                    4  AlPO.sub.4 /Cr.sup.+6                                                                .sup. .sup. 250.sup.(2)                                                             1/2      4 ppm TEB                                                                           3,800 60 1.5                                                                              HL                                 5  AlPO.sub.4 /Cr.sup.+6                                                                600   9/1.sup.(3)                                                                            4 ppm TEB                                                                           2,600 60 .03   155                             6  AlPO.sub.4 /1% F                                                                     600   1/2     None   6,700 60 0  HL                                 7  AlPO.sub.4 /1% F                                                                     600   1/2      4 ppm TEB                                                                           1,000 30                                       8  AlPO.sub. 4                                                                          600   3       10 H.sub.2 (psig)                                                                    4,600 60 .22   29 1,181                                                                            0.9481                                                                            38 6.3                9  AlPO.sub.4                                                                           600   3        5 H.sub.2 (psig)                                                                    3,850 60 .09   22   957                                                                            0.9450                                                                           110 4.3                10 AlPO.sub.4                                                                           600   3       15 H.sub.2 (psig)                                                                    4,362 60 .51   23 1,228                                                                            0.9513                                                                           ≦24                                                                        5.0                11 H.sub.3 PO.sub.4 /Al.sub.2 O.sub.3                                                   600   2       --     8,400 60 0  HL --   579                                                                            0.9259                    12 H.sub.3 PO.sub.4 /Al.sub.2 O.sub.3                                                   600   2       10 H.sub.2 (psig)                                                                    5,100 60 .18   31 1,212                                                                            0.9508                    13 H.sub.3 PO.sub.4 /Al.sub.2 O.sub.3                                                   600   2       50 H.sub.2 (psig)                                                                    3,800 45 11.2  31 1,670                                                                            0.9667                    14 H.sub.3 PO.sub.4 /Al.sub.2 O.sub.3                                                   600   2       25 H.sub.2 (psig)                                                                             .78   58 1,322                                                                            0.9566                    15 SiO.sub.2                                                                            600   5       --     1,900 60 0  HL --   845                                                                            0.9350                    16 SiO.sub.2                                                                            600   1        2 H.sub.2 (psig)                                                                    6,750 60 .04                                                                              HL --   815                                                                            0.9336                    17 SiO.sub.2                                                                            600   1        3 H.sub.2 (psig)                                                                    3,990 60 .31                                                                              HL --   875                                                                            0.9382                    18 SiO.sub.2                                                                            600   2        3 H.sub.2 (psig)                                                                    1,634 60 .02   67 1,080                                                                            0.9464                    19 SiO.sub.2                                                                            600   3        5 H.sub.2 (psig)                                                                    1,136 60 .07   77 1,151                                                                            0.9488                    20 SiO.sub.2                                                                            600   3       10 H.sub.2 (psig)                                                                      138 60 .61   52                              21 SiO.sub.2                                                                            600   3       15 H.sub.2 (psig)                                                                      123 60 2.93  39                              __________________________________________________________________________     .sup.(1) In air unless otherwise specified.                                   .sup.(2) AlPO.sub.4 alone calcined at 600° C. then Cr.sup.+6 added     and activated at 250° C. in CO to give about Cr.sup.+2.                .sup.(3) Cr containing base calcined at 600° C. then added as          separate streams with bis(cyclopentadienyl)chromium(II) at a 9/1 mole         ratio of Cr from the base and chromium from the                               bis(cyclopentadienyl)chromium(II).                                            .sup.(4) 0.002 g/mL.                                                          .sup.(5) Heterogeneity index, M.sub.w /M.sub.n, as determined by size         exclusion chromatography.                                                     .sup.(6) Blanks indicate no data are obtained or not available.          

Run 1 shows a run in accordance with the invention. As can be seen withno special treatments, the catalyst system of the invention is operableto produce polymer at a moderately good productivity. Run 2 shows theadvantage and productivity from the inclusion of a cocatalyst such asthe alkyl boron compound. While there is some scatter in the databecause under the experimental conditions utilized, the chromocenesometimes became contaminated, the data when viewed as a whole shows anadvantage for the use of the cocatalyst. Runs 3 and 4 show that thechromocene can be used with a base which already contains chromium in a+2 state (obtained by reducing chromium +6). Although Run 3 did not giveparticularly good productivity, it was carried out for only 30 minutes.Run 5 shows good melt index obtained by using an aluminum phosphate basecontaining hexavalent chromium in combination with chromocene. Runs 6and 7 show that the base can be fluorided. Run 7 is not believed to be atrue representation of the effective TEB. This run was carried out foronly 30 minutes and in all likelihood the run was either just beginningto polymerize actively when it was terminated or the chromocene wascontaminated in some way. Runs 8-10 show a production of polymer inaccordance with the invention having usable melt index values, andrelatively high productivities. A comparison of Run 10 and Run 21 showsthe greatly improved productivity using thebis-(cyclopentadienyl)chromium(II) with aluminum phosphate as opposed tosilica. Also, a different molecular weight distribution was obtained asis evident by comparing the HLMI/MI ratios. Run 11 shows outstandingproductivity. Runs 12 and 13 show a good combination of highproductivity, usable melt index, and high density.

EXAMPLE VIII

In this example, AlPO₄ produced as in Example I and having a P:Al ratioof 0.9 was calcined at 600° C. It was impregnated (Method B) withbis-(cyclopentadienyl)chromium(II) designated chromocene or dicumenechromium, designated DCC and used without TEB with the followingresults.

                                      TABLE VII                                   __________________________________________________________________________                    Run 1  Run 2  Run 3  Run 4  Control 1                         __________________________________________________________________________    Processing Variables                                                          Reactor Temp. (°C.)                                                                    195    195    195    195    195                               Monomer Feed (mole %)                                                         C.sub.2.sup.=   98.6   98.8   96.2   96.3   100                               C.sub.3.sup.=   --     --     --     --     --                                C.sub.4.sup.=   --     1.2    3.8    3.7    --                                C.sub.6.sup.=   1.4    --     --     --     --                                Others          --     --     --     --     --                                Catalyst                                                                      Aluminum Phosphate                                                                            Yes    Yes    Yes    Yes    Yes                               Cr added via    Chromocene                                                                           Chromocene                                                                           Chromocene                                                                           Chromocene                                                                           DCC                               Polymer Characteristics                                                       Density          0.9218                                                                               0.9202                                                                               0.9201                                                                               0.9195                                                                               0.9383                           MI (HLMI)       *      *      *      *      *                                 MW              UHMW   UHMW   UHMW   UHMW   UHMW                              MWD (By GPC)    **     **     **     **     **                                I.V. ([η])  16.08  16.13  16.06  13.70  ***                               C-13 NMR Results                                                              Apparent Monomer Incorporated                                                 C.sub.2.sup.=  (mole %)                                                                       99.35  99.34  99.22  99.13  99.66                             C.sub.3.sup.=  (mole %).sup.(1)                                                               0.44   0.47   0.49   0.47   0.10                              C.sub.4.sup.=  (mole %).sup.(2)                                                               0.07   0.11   0.21   0.23   0.11                              C.sub.6.sup.=  (mole %).sup.(3)                                                               0.14   0.01   ˜0.08                                                                          0.05   ˜0.13                       Others (mole %) --     ˜0.02   ˜0.11                              Total Branches (mole %)                                                                       0.65   0.66   0.78   0.87   0.34                              __________________________________________________________________________     *HLMI not measurable.                                                         **Samples cannot be run on GPC because of low solubility or solution bein     to viscose.                                                                   ***Sample insoluble.                                                          .sup.(1) i.e., methyl branches. The results look like propylene comonomer     was present in the feed even though none was.                                 .sup.(2) i.e., ethyl branches.                                                .sup.(3) i.e., butyl branches.                                           

As can be seen, an unusual polymer results having ultrahigh molecularweight and a high proportion of methyl branches in the absence ofpropylene comonomer. Thus polymer having at least 0.4 mole percentmethyl branches and ultrahigh molecular weight is possible. Of course,polymer with methyl branches is easily formed using ethylene andpropylene comonomer, but not at this high molecular weight. By molepercent is meant the number of methyl groups based on pairs of carbonatoms in the backbone. That is, a 200 carbon atom chain with 1 methylbranch would be 1 mole percent.

EXAMPLE IX

In this example, chromocene on phosphate is compared with chromocene onsilica.

                                      TABLE VIII                                  __________________________________________________________________________    Run  Catalyst   Monomer Feed                                                                          Molecular Structures Observed and Apprx.              __________________________________________________________________________                            Quantity                                              1    Aluminum phosphate                                                                       C.sub.2.sup.=                                                                         Isolated methyl branches (0.60 mole %                                         C.sub.3.sup.=)                                        2    Aluminum phosphate                                                                       C.sub.2.sup.=                                                                         Isolated methyl branches (0.50 mole %                                         C.sub.3.sup.=)                                        3    Aluminum phosphate                                                                       C.sub.2.sup.=                                                                         Isolated methyl branches (0.41 mole %                                         C.sub.3.sup.=)                                        4    Aluminum phosphate                                                                       C.sub.2.sup.=                                                                         Isolated methyl branches (0.32 mole %                                         C.sub.3.sup.=)                                        5    Aluminum phosphate                                                                       C.sub.2.sup.=                                                                         Isolated methyl branches (0.51 mole %                                         C.sub.3.sup.=)                                        6    Aluminum phosphate                                                                       C.sub.2.sup.=, C.sub.6.sup.=                                                          Isolated methyl branches (0.46 mole %                                         C.sub.3.sup.=)                                        7    Aluminum phosphate                                                                       C.sub.2.sup.=, C.sub.6.sup.=                                                          Isolated methyl branches (0.37 mole %                                         C.sub.3.sup.=)                                        8    Aluminum phosphate                                                                       C.sub.2.sup.=                                                                         Isolated methyl branches (0.38 mole %                                         C.sub.3.sup.=)                                        Control 1                                                                          Silica Cogel                                                                             C.sub.2.sup.=                                                                         Long chain branches (2 per 5 molecules), i.e.,                                less than 0.1 mole percent                            Control 2                                                                          Silia Cogel                                                                              C.sub.2.sup.=                                                                         No branches                                           __________________________________________________________________________

We claim:
 1. A polymerization process comprising:contacting at least onemono-1-olefin having 2 to 8 carbon atoms per molecule in a reaction zoneunder polymerization conditions with a catalyst system comprising:(a) acatalyst comprising a bis-(cyclopentadienyl)chromium(II) compound and aphosphate-containing support; (b) an organometal cocatalyst; andrecovering a polymer.
 2. A process according to claim 1 wherein said onemono-1-olefin is selected from ethylene, propylene, 1-butene, 1-pentene,1-hexene and 1-octene, and said polymerization is carried out underslurry conditions.
 3. A process according to claim 1 wherein said onemono-1-olefin comprises ethylene and said polymerization conditionsinclude a temperature of below 205° F.
 4. A method according to claim 1wherein ethylene polymer having 0.2 to 3 mole percent comonomerincorporation is produced by incorporating 0.5 to 20 mole percentcomonomer in an ethylene feed.
 5. A process according to claim 1 whereinsaid at least one mono-1-olefin olefin includes ethylene and 0.5 to 20mole percent of one of propylene, 1-butene, 1-pentene, 1-hexene, or1-octene.
 6. A method according to claim 1 wherein said support and saidbis-(cyclopentadienyl)chromium compound are introduced into saidreaction zone as separate streams.
 7. A polymerization processcomprising:contacting at least one mono-1-olefin having 2 to 8 carbonatoms per molecule in a reaction zone under polymerization conditionswith a catalyst system comprising:combining an aqueous solution of analuminum salt with a source of phosphate ions and neutralizing with abase to give a hydrogel; converting said hydrogel to a xerogel by one ofazeotropic distillation or washing with a water miscible organiccompound, activating by heating in an oxygen-containing ambient at atemperature within the range of 150°-800° C.; thereafter combining witha bis-(cyclopentadienyl)-chromium(II) compound under anhydrousconditions; and recovering a polymer.
 8. A process according to claim 7wherein said at least one mono-1-olefin is at least predominantlyethylene and said polymerization is carried out under slurry conditions.9. A polymerization process comprisingcontacting at least onemono-1-olefin having 2 to 8 carbon atoms per molecule in a reaction zoneunder polymerization conditions with a catalyst system produced by aprocess comprising:combining an aluminum alkoxide with phosphoric acidto give a hydrogel; converting said hydrogel to a xerogel, activatingthe resulting xerogel by heating at a temperature within the range of150°-800° C.; thereafter combining with abis-(cyclopentadienyl)-chromium(II) compound under anhydrous conditions;and recovering a polymer.
 10. A process according to claim 9 whereinsaid at least one mono-1-olefin is at least predominantly ethylene andsaid polymerization is carried out under slurry conditions.
 11. Apolymerization process comprising:contacting at least one mono-1-olefinhaving 2 to 8 carbon atoms per molecule in a reaction zone underpolymerization conditions with a catalyst system produced by a processcomprising:combining a source of phosphate ions with a melt of analuminum salt; neutralizing to give a hydrogel; converting said hydrogelto a xerogel, activating the resulting xerogel by heating to atemperature within the range of 150°-800° C.; thereafter combining witha bis-(cyclopentadienyl)-chromium(II) compound under anhydrousconditions; and recovering a polymer.
 12. A process according to claim11 wherein said at least one mono-1-olefin is at least predominantlyethylene and said polymerization is carried out under slurry conditions.13. A method according to claim 11 wherein said xerogel after activationand said bis-(cyclopentadienyl)chromium(II) compound are introduced intosaid reaction zone as separate streams.
 14. A method according to claim11 wherein said olefin comprises ethylene and said polymerizationconditions include a temperature of below 205° F.
 15. A polymerizationprocess comprising:contacting at least one mono-1-olefin having 2 to 8carbon atoms per molecule in a reaction zone under polymerizationconditions with a catalyst system produced by a processcomprising:treating a silica-containing material with a phosphatingagent selected from phosphate ions and vaporized phosphorus compounds soas to give 0.001 to 0.2 gram atoms of phosphorus per mole of silica;activating the resulting treated silica at a temperature of 150°-800°C.; thereafter combining with a bis-(cyclopentadienyl)-chromium(II)compound under anhydrous conditions; and recovering a polymer.
 16. Apolymerization process comprising:contacting at least one mono-1-olefinhaving 2 to 8 carbon atoms per molecule in a reaction zone underpolymerization conditions with a catalyst system produced by a processcomprising:cogelling silica and aluminum phosphate to form a hydrogel;removing water from said hydrogel to form a xerogel, activating theresulting xerogel by heating at a temperature within the range of150°-1000° C.; thereafter combining with abis-(cyclopentadienyl)-chromium(II) compound under anhydrous conditions;and recovering a polymer.
 17. A polymerization process according toclaim 16 wherein said at least one mono-1-olefin is at leastpredominantly ethylene and said polymerization is carried out underslurry conditions.
 18. A polymerization process comprising:contacting atleast one mono-1-olefin having 2 to 8 carbon atoms per molecule in areaction zone under polymerization conditions with a catalyst systemproduced by a process comprising:impregnating silica with aluminumphosphate by combining a source of aluminum ions and phosphate ions witha slurry of silica in a diluent; thereafter forming said aluminumphosphate by evaporating the diluent, activating the thus-impregnatedsilica by heating at a temperature within the range of 150°-1000° C.;thereafter combining with a bis-(cyclopentadienyl)-chromium(II) compoundunder anhydrous conditions; and recovering a polymer
 19. Apolymerization process comprising:contacting at least one mono-1-olefinhaving 2 to 8 carbon atoms per molecule in a reaction zone underpolymerization conditions with a catalyst system produced by a processcomprising:impregnating a silica xerogel with boron phosphate by addinga source of boron ions and a source of phosphate ions to a slurry ofsilica xerogel in a diluent; thereafter evaporating the diluent,activating the thus-impregnated silica by heating at a temperature of150°-800° C.; thereafter combining with abis-(cyclopentadienyl)-chromium(II) compound under anhydrous conditions;and recovering a polymer.
 20. A polymerization processcomprising:contacting at least one mono-1-olefin having 2 to 8 carbonatoms per molecule in a reaction zone under polymerization conditionswith a catalyst system produced by a method comprising:precipitatingaluminum phosphate in the presence of silica-alumina; activating theresulting xerogel by heating in an oxygencontaining ambient at atemperature within the range of 150°-1000° C.; thereafter combining witha bis-(cyclopentadienyl)-chromium(II) compound under anhydrousconditions; and recovering a polymer.
 21. A polymerization processcomprising:contacting at least one mono-1-olefin having 2 to 8 carbonatoms per molecule in a reaction zone under polymerization conditionswith a catalyst system produced by a process comprising:activating asilica-alumina xerogel by heating in an oxygen-containing ambient at atemperature within the range of 150°-1000° C., activating an aluminumphosphate xerogel by heating in an oxygen-containing ambient at atemperature within the range of 150°-800° C.; thereafter combining abis-(cyclopentadienyl)chromium(II) compound with said thus activatedsilica and said thus activated aluminum phosphate, said silica andaluminum phosphate either being physically mixed prior to saidactivation or combined subsequent to said activation; and recovering apolymer.
 22. A polymerization process comprising:contacting at least onemono-1-olefin having 2 to 8 carbon atoms per molecule in a reaction zoneunder polymerization conditions with a catalyst system produced by aprocess comprising:phosphating an alumina-containing composition bytreating same with a phosphating agent selected from (1) phosphate ionsand (2) vaporous phosphorus compounds to give a surface compositionhaving a 0.2:1 to 1:1 P/Al atom ratio; activating said thus phosphatedalumina composition by heating in an oxygen-containing ambient at atemperature within the range of 150°-800° C.; thereafter combining witha bis-(cyclopentadienyl)-chromium(II) compound under anhydrousconditions; and recovering a polymer.
 23. A process according to claim22 wherein said at least one mono-1-olefin is at least predominantlyethylene and said polymerization is carried out under slurry conditions.24. A polymerization process comprising:contacting at least onemono-1-olefin having 2 to 8 carbon atoms per molecule in a reaction zoneunder polymerization conditions with a catalyst system produced by aprocess comprising:forming an aluminum phosphate hydrogel, contactingsaid hydrogel to a xerogel by azeotropic distillation or washing with awater miscible organic liquid; activating by heating at a temperaturewithin the range of 150°-800° C.; thereafter combining with abis-(cyclopentadienyl)-chromium(II) compound under anhydrous conditions;and recovering a polymer.